1. Technical Field
This invention relates to an improved utility knife and more particularly relates to a knife in which the cutting blade is automatically retracted safely inside of the knife handle when an operating lever of the knife is released by the user.
2. The Prior Art
Most utility knives employing standard commercial cutting blades have the blade fixed in a use position and require positive action by the user to separate the blade from its carrier or handle, or to retract the blade when retraction means are provided. Such utility knives with exposed blades cannot be carried in the pocket or tethered to the user, since the exposed blade can cause damage or injury under these circumstances.
Utility knives are also known in which the blade is extended to a use position by cam action and is retracted by spring action to an enclosed position. These latter types of knives include no means other than the hand of the user to lock the blade in the extended use position and, consequently, forces on the blade during use, such as opening cartons, are transmitted to the hand. This is somewhat awkward and tends to render the knife unstable during use.
Therefore, a major object of the invention is to provide a safe utility knife including means cooperating with the hand of the user to lock the blade rigidly in the extended use position whereby forces on the blade are not felt by the hand of the user, and the knife is rigid and stable during heavy usage.
A further and more specific object of the invention is to provide a safe utility knife in which an extensible and retractable blade is operated by a simple toggle mechanism which assumes a straight line dead center blade locking position when the blade is extended for use, the toggle mechanism being connected with a hand lever pivotally attached to the knife handle.
Other features and advantages of the invention will become apparent to those skilled in the art during the course of the following detailed description.